public object Eval(TextReader str)
{
//Console.WriteLine("starting eval");
Object evaledObj = null;
Object parsedObj = Util.read(str);
if (parsedObj is Pair)
{
if (macros.Count > 0)
{
// bool curRunHidden = DebugInfo.RunHidden;
// DebugInfo.RunHidden = true; //don't debug the macro expension code
Closure macroExpand = initEnv.Apply(Symbol.Create("macro-expand")) as Closure;
parsedObj = macroExpand.Eval(new Object[] { parsedObj });
// DebugInfo.RunHidden = curRunHidden;
}
Pair p = parsedObj as Pair;
switch (p.car.ToString())
{
case "define":
Expression expr = null;
Symbol def = null;
if (p.cdr.car is Pair) // (define (fn x y) body)
{
Pair def_and_args = p.cdr.car as Pair;
Pair body = p.cdr.cdr;
Pair syms = def_and_args.cdr;
def = Symbol.Create(def_and_args.car.ToString());
expr = Expression.Parse(Pair.Cons(Symbol.Create("lambda"), Pair.Cons(syms, body)));
// Debug.WriteLine(def + "-->" + expr);
}
else // (define fn (lambda (x y) body))
{
def = Symbol.Create(p.cdr.car.ToString());
expr = Expression.Parse(p.cdr.cdr.car);
}
//initEnv = new Extended_Env(new Pair(def), new Pair(null), initEnv);
//Object value = Eval(expr);
//Console.WriteLine("defining: " + def);
// expr.Mark(p);
initEnv.Bind(def, Eval(expr));
break;
case "macro":
Symbol name = p.cdr.car as Symbol;
// Console.WriteLine("macrodef" + name + " " + Expression.Parse(p.cdr.cdr.car).Eval(initEnv).ToString());
Closure transformer = (Closure)Expression.Parse(p.cdr.cdr.car).Eval(initEnv);
this.macros[name] = transformer;
// Console.WriteLine("macro: " + name);
break;
default:
// need to call macro-expand in here. but how?
evaledObj = Util.Dump(Eval(Expression.Parse(parsedObj)));
break;
}
}
else
{
evaledObj = Util.Dump(Eval(Expression.Parse(parsedObj)));
}
if (str.Peek() == -1)
{
return(evaledObj);
}
else
{
return(Eval(str));
}
}
public A_Program()
{
this.initEnv = new Extended_Env(new Symbol[] { Symbol.Create("_macros") }, new Object[] { macros }, Env.The_Empty_Env);
} // new Pair(new Symbol("x")), new Pair(3), Env.The_Empty_Env);}